FIG. 18 shows a prior art stereoscopic observation device disclosed in Japanese Laid-open Patent Application No. 51-24116 that includes a concave mirror ME, and facing this, right and left concave mirrors MPR, MPL, and right and left image display devices PR, PL arranged as illustrated so that an observer can view three-dimensional images from the right and left eye positions ER, EL, respectively.
FIG. 19 is a side view of the stereoscopic observation device of FIG. 18 having been flipped upside down, for convenience of explanation. The viewing pupil positions ER, EL of the right and left eyes, the positions of each image ER′, EL′ formed by the concave mirror ME for both eyes, and the positions of each image ER″, EL″ formed by the concave mirrors MPR, MPL are illustrated. Also shown is the center of curvature C of the concave mirror ME and the centers of curvature CPR, CPL of the concave mirrors MPR, MPL.
However, with the above-described, well-known device, concave mirror manufacturing costs and installation costs are high because image distortion will easily result due to any of installation errors, profile irregularities in the concave mirror, and large variations in the focal position. Furthermore, if the viewing position of the observer is offset from the specified position, the image will become greatly distorted, and thus the observation posture and observation position are limited. Therefore, handling the stereoscopic observation device is inconvenient during observation. The exit pupil may be enlarged in order to increase the positioning freedom during observation. However, in order to enlarge the exit pupil in this stereoscopic observation device, the concave mirror must be enlarged. Therefore, the overall size of the device increases.